The invention relates generally to sensors, and more particularly to systems and methods for interrogating radio frequency identification (RFID) sensors.
Generally, RFID readers are used to obtain digital data from RFID tags. Digital data may include, for example, digital identification of the tag, or any other information written and/or stored in a memory chip of the RFID tag. The RFID tags transmit electromagnetic signals at different relative levels of transmitted power at different times. Signals received by the RFID reader in combination with the transmitted relative power level of the received signals are employed to locate the RFID tags, and read the digital identification information from the RFID tag (e.g., from the memory chip or back-reflector structure of the RFID tag).
When the RFID tags are used in RFID sensors, separate readers are used to read the analog (e.g. sensing parameters) and digital (e.g. tag ID, stored user information) data from the RFID sensors. In cases where digital data as well as analog data are obtained from the RFID sensors, two different readers need to be employed. Use of two different readers increases the complexity, size and cost of the system.
Therefore, it is desirable to have an integrated interrogation system for RFID sensors that can read both digital and analog data from the RFID sensors.